Welding parts heat treatment and welding parts technical requirements

Welding heat treatment; 1. Pre-heat treatment: Pre-heat treatment is the overall or partial heating of structural parts before welding. The purpose is to slow down the temperature gradient and cooling rate of the welded joint during heating, and appropriately extend the cooling time of the welded joint from 800°C to 500°C, so as to facilitate the escape of hydrogen in the weld, reduce the production of hardened structures, and prevent cold cracks The production. In addition, the overall preheating of the components can appropriately improve the uniformity of the temperature distribution of the weldment and reduce the internal stress.　　The preheating temperature can be determined by empirical formulas, or you can refer to relevant experimental data. It should be noted that these calculation formulas or experimental data are established under certain test conditions and based on the minimum preheating temperature that does not produce cracks. Therefore, special attention should be paid to the scope of application when selecting to avoid unnecessary losses. Too high preheating temperature will not only increase the cost, but also worsen the working conditions of the welder. Therefore, under the condition that the process requirements can be met, a lower preheating temperature should be used as much as possible. In order to prevent delayed cracks when interlayer heating is performed on multilayer welded components, the interlayer temperature should not be lower than the preheating temperature, otherwise the delayed cracks cannot be effectively prevented.　　2. Post heat treatment: After the welding is stopped, the preheating device is used to heat the weldment or the welding area immediately and keep it for a certain period of time. The purpose is to make the hydrogen in the weld metal escape sufficiently to prevent cracks. In practical applications, for low-alloy steels with higher strength grades and welded components with larger thicknesses, post heat treatment has a more obvious effect on preventing cracks.　　 Choosing a reasonable post-heat treatment temperature can reduce the preheating temperature to a certain extent (usually it can be reduced by 50°C), or even cancel the preheating. Lowering the preheating temperature is conducive to improving the working conditions of workers, increasing production efficiency, reducing the energy consumption of linear guides, and reducing the chance of defects such as thermal cracks due to excessive preheating temperature.　　3. Post-weld heat treatment: Post-weld heat treatment is the overall or partial heat treatment of the welded components after the welding is completed. Its purpose is to improve the structure and performance of the metal, reduce the welding residual stress, soften the hardened structure of the welding heat-affected zone, and improve the general treatment of the welded joints and toughened stampings; 1. The shot peening of the welded parts is to prevent steel shots from drilling For welds, the inner welds must be welded, and the inner city and cavity must be avoided as much as possible. If the inner city and cavity are necessary in the structure, it must be pickled in order to achieve the surface derusting quality.　　2. Welding parts made of ordinary low-alloy structures must be pre-heated and post-welded in accordance with the carbon equivalent and alloy element content of the welded parts, the thickness of the parts, the purpose and requirements of the steel structure. 3. For welded parts with a sealed inner cavity, before heat treatment, a Φ10mm hole should be machined in an appropriate position on the intermediate partition plate to make the cavity communicate with the outside world. If the outer wall needs to be drilled, it should be plugged again after heat treatment. . 4. The radiographic flaw detection of welds should meet the requirements. For welding to be subjected to mechanical performance tests, it should be indicated in the drawings or technical requirements of the order. The mechanical performance test types and sample sizes of the welds should be in accordance with the regulations. The sample plate should be welded to the workpiece after welding. After the same heat treatment, and through the appearance of non-destructive inspection in advance.　　5. When the weldment is to be tested for tightness and pressure test, it shall be carried out in accordance with the requirements of this standard. When pressure test is required, the test pressure and pressure test time shall be indicated in the drawings or order requirements. Related news: The characteristics of the main materials of stamping parts, the treatment of common problems of stamping parts, the characteristics of scaffolding stamping parts and the importance of inspections